(a) Field of the Invention
The present invention relates to a portable data-processing terminal and, more particularly, a portable data-processing terminal, such as cellular phone and portable data assistant, having a function for managing the competition between a plurality of tasks.
(b) Description of the Related Art
Portable data-processing terminals such as a cellular phone are widely used in the daily life of the majority of people. A cellular phone, for example, has a plurality of task programs for controlling a plurality of tasks, such as call originating task for originating a call, call accepting task for accepting a call based on a radio signal transmitted from a base station. The cellular phone has also other programs which are not directly involved with the telephone functions, such as a schedule alarm program or a low-voltage alarm program.
The plurality of tasks controlled by the task programs are categorized in a few types including first type which is started by the input operation of the keyboard by the user, second type which is started by the radio signal transmitted from the base station, third type which is started automatically at a specified time interval etc. These tasks are started at respective timings independent of each other, although these tasks may use a common lower-level functional block or unit, such as a receiving block, transmitting block, display unit, or a speaker.
Thus, a competition between a plurality of tasks sometimes arises in the cellular phone, wherein the plurality of tasks use the common lower-level function. For avoiding such a competition in a conventional technique, each task or task program recognizes the status of the other tasks or task programs using the common lower-level functional unit. Such a competition can be avoided, if a task, which is to use a specific lower-level functional unit, recognizes the status of other tasks and delays the use of the specific lower-level functional unit by forecasting a competition.
In the conventional technique for avoiding the competition, as described above, there is a problem in that each program should have an additional program part for avoiding the competition in addition to the program body used for achieving the own inherent task thereby causing an increased size of the program. In addition, if a new task program is added to the existing task programs, the existing task programs must be revised due to the change of the competition conditions. The work for the revision of the programs increases the costs of the cellular phone.